Lighting Design by DETAIL

â&#x2C6;&#x201A; Practice

Lighting Design Principles Implementation Case Studies

ULRIKE BRANDI LICHT

Edition Detail

Authors: Christina Augustesen, Architect Ulrike Brandi Licht GmbH, Hamburg Ulrike Brandi, Director Ulrike Brandi Licht GmbH, Hamburg Udo Dietrich, PhD Büro für Bauphysik, Gebäudesimulation und Integrales Planen, Hamburg Annette Friederici, MA Cultural Studies Ulrike Brandi Licht GmbH, Hamburg Christoph Geissmar-Brandi, PhD Ulrike Brandi Licht GmbH, Hamburg Peter Thule Kristensen, Architect, PhD Assistant at the School of History and Theory of Architecture, School of Architecture – Royal Danish Academy of Fine Arts, Copenhagen Merete Madsen, Architect, PhD Assistant at the School of Daylight Research, School of Architecture – Royal Danish Academy of Fine Arts, Copenhagen, Anja Storch, Lawyer/Mediator, Hamburg Burkhard Wand, Dipl.-Ing. Ulrike Brandi Licht GmbH, Hamburg Editor: Andrea Wiegelmann, Dipl.-Ing. Editorial Staff: Nicola Kollmann, Dipl.-Ing. Christina Schulz, Architect Drawings: Andrea Saiko, Dipl.-Ing. Translation: Caroline Ahrens, Esther Mallach p. 84 – 89 © 2006 Institut für internationale Architektur-Dokumentation GmbH & Co. KG, Munich An Edition DETAIL book ISBN-10: 3-7643-7493-4 ISBN-13: 978-3-7643-7493-8 Printed on acid-free paper made from cellulose bleached without the use of chlorine. This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the right of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in databases. For any kind of use, permission of the copyright owner must be obtained. Typesetting and production: Peter Gensmantel, Andrea Linke, Roswitha Siegler, Simone Soesters Printed by: Aumüller Druck KG, Regensburg This book is also available in a German language edition (ISBN 3-920034-12-0). A CIP catalogue record for this book is available from the Library of Congress, Washington D.C., USA

Bibliographic information published by Die Deutsche Bibliothek Die Deutsche Bibliothek lists this publication in the Deutsche Nationalbibliographie; detailed bibliographic data is available on the internet at http://dnb.ddb.de Institut für internationale Architektur-Dokumentation GmbH & Co. KG Sonnenstrasse 17, 80331 Munich, Germany Tel.: +49 89 38 16 20-0 Fax: +49 89 39 86 70 Internet: www.detail.de Distribution Partner: Birkhäuser – Publishers for Architecture P.O. Box 133, CH-4010 Basel, Switzerland Tel.: +41 61 205 07 07 Fax: +41 61 205 07 92 email: sales@birkhauser.ch http://www.birkhauser.ch

∂ Practice Lighting Design

Introduction

Daylight and Well-Being

Daylight – Characteristics and Basic Design Principles

Daylight Control

48 48 52 57

Lighting Design Public Utility Company Schönebeck Light and Shadow – Design of a Church New Mercedes Benz Museum

Light Control: a Part of Facility Management

Procedure for Planning Artificial Light in Buildings

The Lighting Designer’s Position from a Contractual Point of View

Daylight as a Building Material

102 104 106 112

Standards and Regulations Bibliography Directory of Manufacturers and Organisations Photo credits

Can one design light? The free internet encyclopaedia Wikipedia, currently one of the most topical and intriguing collections of knowledge, states in its German version: “Planning is the intellectual process of creating a design with elements of varying relative and intrinsic significance: the applications and the comprehension of planning are thus also variable. As a central tenet, the essence of planning can be described as the bringing into being of concepts that are both target-oriented and value-assessed. If planning is to be of practical use, two further criteria must be fulfilled: it must be based on existing or feasible resources to allow for its realisation, and it must be allotted a timescale within which it is to be either realised or abandoned. The purpose of planning is to create clarity. Planning, the creation of target-oriented, value-assessed concepts with regard to time and resources, is carried out for the purpose of optimising the progression of a future series of events. (Linked) examples are: landscape architecture, urban planning, regional planning, development control planning and construction planning.” How does this apply to the planning of light? ibidem: “Light is that part of electromagnetic radiation that is visible to the human eye, the electromagnetic waves within the frequency range 380–780 nanometre (750 nm: red, 400 nm: violet/blue). The visible spectrum is part of the electromagnetic spectrum. The differing sensitivities of pigment molecules (blue, green-yellow, orange-red) in the rod cells of the human eye to different wavelengths forms the basis of photometry. While cone cells are responsible for colour vision, rod cells in the retina register the luminous intensity by means of splitting rhodopsin within the retinal molecules on reception of light photons...” Is this the sole frame of reference for the planning of light? The first comprehensive German encyclopaedia, Zedlers Lexikon, “the large complete universal encyclopaedia of all sciences and arts, that have hitherto been invented and improved by the human mind and wit (...) Leipzig 1732” takes a different standpoint. There is no entry for planning, but the following for light: 6

“Licht, ist vornehmlich zweyerley Art Licht, Lat. Lux Licht, Kertze Licht, wird in heiliger Schrifft genennet Licht heisset bey dem Baue die öffnung Licht, das helle Theil eines Gemählde Licht, ein brennendes und scheinendes war Licht, der Dämmerung ähnliches Licht, ewiges Licht, Stärckedesselbigen Licht, da niemand zukommen kann, darinen Licht, das da scheinet in einem dunckeln Licht hieß Gott aus dem Finsterniß hervorleuchten Licht ist dein Kleid Licht ist Gott Licht ist noch eine kleine Zeit bey euch Licht ist süß Licht kommet, dein Licht lasset leuchten vor denen Leuten, ec. Licht des Lebens Licht meiner Augen ist nicht bey mir Licht muß dem Gerechten immer wieder Licht scheidete Gott von der Finsterniß, ec. Licht scheinet in der Finsterniß Licht versäumen Licht wird’s seyn um den Abend Licht und Heil ist mir der Herr, vor wem ec. Licht und Recht Licht der Welt seyd ihr Licht vom Himmel erleuchtete Licht werden Licht wird hervor brechen wie die MorgenRöthe” Light has many meanings Light, Latin lux Light from candles Light is referred to in the Holy Bible Etc. etc. This collection of knowledge finds manifold poetic expressions to describe the phenomenon of light. In total the author lists 32 incidences of light in the encyclopaedia. One can sense how far light dominated life in those days and how it was synonymous with human life and nature. Hence, his final sentence is: “Light will erupt like dawn”. This conception is still easier to understand. The authors of this book are in fact describing the conceptual uses of daylight and artificial light in today’s building processes, beginning in the 20th century. For this reason, we have begun our overview with the last chapter of this volume. Merete Madsen and Peter Thule Kristensen draw on examples to chronologi-

cally trace the use of daylight as a building material in the 20th and early 21st century. Anja Storch, a lawyer specialising in planning law, writes about the dominating role of costs and contracts in the planning process. The latest event in the musefication of the automobile is to be found at the new Mercedes Benz Museums in Stuttgart, designed by UN-Studio, combining artificial exhibition lighting with natural illumination. A brief guide to the procedures of designing artificial light is included. Case studies describe the necessary steps, from the first considerations of light in a building to the completed project design. The previous chapter examines new trends in lighting design in the context of the interdisciplinary automation of buildings. In her analysis of a church, Christina Augustesen shows how light and shadow can be the central defining elements of spaces. The combined use of natural and artificial light as a means of reducing energy consumption while increasing comfort levels was a requirement of the design brief for a new public utilities building in Schönebeck. The case study introduces the relevant systems and components. Udo Dietrich explains in his long and coherent piece how daylight can be integrated into the design of new developments – a practical summary, not seen before in this form. And finally, natural light has a great bearing on our well-being, as Annette Friederici and Burkhard Wand describe in their article. We hope the book will help to create more awareness for the use of light in architecture. Hamburg, May 2005 Ulrike Brandi Christoph Geissmar-Brandi

Right: Galerie de L’Evolution, Museum of Natural History, Paris, renovation 1994 Not implemented was the design for a daylight ceiling that projected the path of the sun in different seasons to create changing light ambience in the interior. The final proposal utilises artificial light to protect the exhibits (see pp. 82/83).

Daylight and Well-Being Annette Friederici Burkhard Wand

No life without light From birth, man strives towards light. It is the basis of all existence on our planet. Without light we cannot breathe, nor see or perceive colour (Figure 1). As the source of energy for photosynthesis, light is the primary source of life for man. Via the sensory system it controls the processing activities of important information. Furthermore, life science research has identified the photo-biological characteristics of light and emphasised its role in human well-being. The visual system, in complex processes, enables not only our spatial orientation but also controls motoric and hormonal activities which help the development of our threedimensional perception. Knowledge about the effects of daylight – as a controlling element of various psycho-physiological processes in organisms – has changed and expanded established concepts of daylight planning in buildings. This necessitates an integrated approach incorporating aspects of architecture, lighting technology and life science. Psychological effects of daylight Human dependency on light and the positive effects of natural light on our health becomes apparent only when we are deprived of light or exposed to excess quantities of light. Through the human eye and skin photobiological processes are triggered which have an effect on our physical and psychological constitution. Poor light conditions lead to fatigue of the eyes and brain (Figure 2). The type of light also influences the psychological constitution of man. A well known example of this is the influence of daylight with respect to its seasonal progression. Short, dull days in winter often have a negative effect on our mood. Studies by the Research Foundation of Lighting and Health in the Netherlands have 8

shown that roughly 70 % of the population feel minor depressive mood swings. They also confirmed that additional light at the workplace relieves these symptoms which, in turn, has a positive effect on well-being, and hence on performance. Scientists call the chronic form of winter depression Seasonal Affective Disorder (SAD); approximately 3 % of the population are affected. It can be successfully treated with a light therapy during the dark winter months. Light is the most important time regulator of the human biorhythm. The alternation of day and night brought about by the rotation of the earth in a 24-hour cycle (circadian rhythm) activates the production of hormones in the human body (Figure 3). Recent scientific studies have found that the circadian rhythm influences our sense of time much more than social factors such as working or eating rhythms. The pineal gland’s secretion of the hormone melatonin (sleeping hormone) is determined by the illumination level, the length of exposure and the spectral composition of the light reflected onto the retina. In work environments the optimisation of production processes has led to extending working hours into the night (more efficient use of production facilities) and to building workplaces largely without windows (maximum area utilisation and production optimisation). Artificial lighting systems were developed and replaced daylight with static light. This, however, cannot compensate for a lack of ultraviolet rays or the liveliness of sunlight (Figure 5 a, b). One of the diseases typical of recent times is rickets, caused by a lack of sunlight. Insufficient levels of ultraviolet sunlight (280 nm – 320 nm) reduces the human skin’s production of vitamin D, which regulates the absorption of calcium from food and its uptake by the bones. The result is the softening of the bones which can lead to

Daylight and well-being

Time of day

cessation of growth, or even bone deterioration. The lack of daylight is second only to airconditioning as the leading cause of SBS, Sick Building Syndrome. The World Health Organisation coined the term in 1983 to describe the negative effects of the built environment that are not related to a specific physical illness. A study by A. and G. Çakir proved that the typical symptoms of SBS – headaches, fatigue, numbness and irritation of the eyes – increase in proportion to the use of artificial lighting. The ailments increase the further the workplace is located towards the centre of the room, while higher levels of daylight have shown to improve performance. In addition the phenomenon of psychological glare suggests that artificial lighting, even if it is installed to standard specifications, cannot replace the quality of daylight. Psychological glare is the manifestation of a subjectively felt disturbance caused by a great disparity of light intensity in the field of vision. Glare caused by brightly lit surfaces, or luminaires themselves, can impair our visual performance and contribute to deterioration in our well-being, while generally, we perceive glare caused by sunlight as pleasant. The reason for this is not yet known, but it can be presumed that glare from daylight is less disturbing because it also conveys information (time of day, season, weather conditions, etc.). Qualities of natural light What distinguishes daylight from artificial lighting? What are its specific qualities? The trend continues in which the human being is exposed to only a fraction of the daylight a life in closer contact with nature would provide. In many situations we instinctively turn towards daylight: when we look out of the window in the office, or

Melatonin

Alertness 4

draw the first breath upon leaving artificially lit, windowless rooms. The standard illuminance of 500 lx at the workplace is sometimes perceived as too bright, whereas out-of-doors 5 000 lx seem pleasantly dark. This example illustrates where the deficits of entirely artificially lit spaces lie. The dynamics of daylight have a stimulating effect on us. Light is modulated in many ways, deformed and structured, before being reflected onto the retina, as light carrying secondary information. We never see the total amount of light hitting an object (illuminance), but only the light reflected at a specific point (luminance), the amount and composition being determined by the properties of the lit surface (see also pp. 17, 18). We receive information about the shape, colour and spatiality of our surroundings from brightness and colour contrasts (Figure 7). Resultant are the following dynamic components of daylight which are dependant upon the spectral transparency of the atmosphere of the location (changing climatic conditions, particle content of the air) and the respective seasonal and daily path of the sun.

ultraviolet light

infravisible red light ca. 380–780 nm light sensitivity of a solar cell ca. 350–1100 nm

spectral intensity (W/m 2*nm)

Cortisol

solar radiation outside the earth’s atmosphere

2.0

solar radiation at sea level at a vertical angle

1.5

emission curve of a black body at 5900 K

1.0

diffuse section at a moderately overcast sky diffuse section at a clear sky

0.5 0

5a 1

3 4

Sunflowers, turned towards the sun. Without light we cannot breathe, cannot see or perceive colours. Poor lighting conditions lead to fatigue of the eyes and mind. We can no longer concentrate, letters swim in front of our eyes, and words turn into hieroglyphs. 2 ≈ 24-hour diagram of different circadian rhythms in the human body Light pollution at night in the port of Hamburg. In large industrialised nations night is turned into day by artificial light. This disturbs the ecological and biological equilibrium. a Spectral composition of sunlight b Spectrum of a fluorescent lamp without UV-B radiation

watt/(sr ≈ 5 nm ≈ 1000 cd)

400

800 1200 1600 2000 2400 (nm)

0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 350 400 450 500 550 600 650 700 750 800 (nm)

Qualities of natural light

Brightness As a consequence of these previously mentioned influences, the outdoor illuminance can vary between levels exceeding 100 000 lx on a sunny summer’s day, to below 5 000 lx on a cloudy day in winter. We refer to a variation in the brightness of daylight although what we really see is the luminance of the surface onto which the light falls. These absolute, quantifiable values (luminance in candela per m2) are only of minor importance to our perception of brightness. How bright or how dark we perceive an area to be does not depend on the inten-

sity of the physical stimulus (luminance). It is always the relative brightness of different areas to one another that triggers a sensation of brightness. The following example illustrates this: If one looks at a dark building facade in direct sunlight and a white sheet of paper on a desk lit to standard specification, the physical sensation caused by the dark building facade will be much more intense than that by the paper (Figure 6 a, b). But the facade looks black and the paper white, because in the first case we have a relatively weak stimulus

blue sky: 4 000 cd/m2

overcast sky: 6 000 cd/m2

sun: 1600 000 000 cd/m2

illuminance of the overcast sky: 5 000 –20 000 lx illuminance of sunshine: 20 000 –100 000 lx 7

Daylight and well-being

in very bright daylight and in the second, the strongest possible stimulus in artificial light. Colour and the spectral composition of daylight The sun is the source of natural light. Sunlight entering the earth’s atmosphere is scattered mainly in the range of the shortwave blue end of the spectrum. This is why the sky looks blue. Depending on the weather conditions it may look white-grey with an overcast sky (~5 000 K) or clear blue with a cloudless sky (~100 000 K). Sunrise and sunset appear red to us because the light must travel a longer distance through the denser strata of the atmosphere closer to the surface of the earth. The blue part of sunlight is scattered while mainly the long-wave light (red) passes through. Despite different colour temperatures (measured in K = Kelvin), we perceive daylight as being more or less white. It seems that our visual system can assess the spectral properties of the incoming rays and compensate for its effect on the appearance of objects. This phenomenon of perception is called colour constancy (Figure 8 a–c).

Light direction Daylight can be subdivided into directed light (near parallel light with an apex angle of only 0.5°) and diffuse light from the sky (scattered light) occurring on days with a clear or overcast sky. Shadows, determined by the effects of contrast, are also a product of the light direction (next to other influences, such as type of light, environment and observer). Shadow is an important factor in the perception of space and objects. Depending on the proportion of directional sunlight and diffuse daylight, one can, apart from dark-light contrasts, observe coloured shadow on lit objects, with the colour tone corresponding to the complementary colour of the light (Figure 9).

a, b If one looks at a dark building facade in direct sunlight and a white sheet of paper on a desk lit to standard specification, the physical sensation caused by the dark building facade is much more intense than that by the paper, but the facade looks darker and the paper bright white. Examples of the luminance of the sky (cd/m2) and related illuminance (lx) on the ground. However, we do not perceive illuminance as brightness, but as luminance. This is the part of light from the sky and sunlight that is reflected by the objects onto which it falls and then to the eye. At an equal illuminance on the ground we perceive daylight, as different levels of brightness (luminance) depending on the reflective properties of the surface lit. The grass looks darker than the water – under an overcast sky there is less contrast than in sunshine. a Object in daylight (blue tinge) b Object in artificial light (yellow tinge) c Object as perceived by the human eye. Claude Monet, Grainstack, 1891. The painting shows the coloured shadows described in the text.

Daylight Control Ulrike Brandi

During the past two decades daylight planning has been established in the performance profile of lighting designers. Clients and architects are starting to understand the influence of daylight, in all its facets. Today, teams of specialists design building skins: architects, HVAC engineers and energy consultants, facade and lighting designers. We, the lighting designers, simulate the proposed building geometry, either with models and an artificial sky, or by using simulation software. Both of these tools have advantages and disadvantages, but can be used to complement one another. During the past 20 years, daylight has also become an important consideration for engineers. The drive to save energy has set off a search for ways to maximise the effective use of daylight while at the same time reducing the associated – in most cases unfavourable – thermal radiation. The recent association of the two disciplines of daylight planning and indoor climate technology has yet to be put into architectural practice – an interesting prospect. In addition to the ecological and economic advantages of a good supply of daylight in a building, planned use of natural light enhances design and has a positive effect on the physical and psychological well-being of its users. The qualities of natural light are irreplaceable. Hence, examining the existing daylight conditions should be the starting point of every artificial lighting scheme. The first clues will be derived from the building’s orientation, its location and surroundings, and the shading to which it will be subject. The requirements of a building will differ according to its geographic location: in northern latitudes, where there is less available sunlight and warmth, the extensive utilisation of light is essential. The closer we are to the equator, the more daylight there is and the more closed-off the architecture will be.

Principles of daylight systems Apart from the significant effect daylight has on the landscape and on urban spaces, it also determines the authentic site of a building. For this reason, it is of utmost importance to engage architects and clients in a detailed discussion on the intended role of daylight. Well-planned, imaginative use of daylight will strengthen the character of a building and create a unique atmosphere that will change through the course of a day and through the seasons while serving a wide range of functions. Initially it is helpful to establish the most extreme solar radiation conditions, at noon throughout the year, and at dawn and dusk. In addition, different weather conditions have to be taken into account: bright sunlight, overcast sky, fog, twilight, brilliant autumn weather, thunderstorms, rain or snow. In some instances the sun needs to be filtered out, in others the natural light needs supplementing with artificial light. Changing light conditions have a positive influence on the well-being of people (see p. 8f). For many years, attempts have been made to set a standard for ergonomically “correct” lighting. This has led to a monotonous uniformity of illuminance levels and

Daylight control

1 2 3 4, 5 6

a reduction in contrasts and reflectance, especially in offices. Today, we increasingly design for dynamic lighting situations, even in office spaces, integrating as much daylight as possible. Studies of people’s waking and sleep rhythms, and health problems such as SAD (Seasonal Affective Disorder) common in northern latitudes, SBS (Sick Building Syndrome) and ADD (Attention Deficit Disorder) found that the supply of sufficient daylight is vital. Daylight is far superior in quality and intensity to artificial light; on sunny days we will find 10 000 to 100 000 lux outdoors. A further characteristic affecting people is the varying spectral composition of light. Traditional methods of controlling and deflecting daylight are often simple but compare well with many of the technically complex systems created during the last twenty years. A deep, white painted window soffit deflects daylight into the room. Even the glazing bars of old windows will deflect light onto the ceiling of an interior space – and these windows, despite their comparatively small glazed area, are, in terms of daylight, only slightly less effective than larger windows. A pool of water adjacent to a building will reflect daylight into the interior (Figure 1a).

Light shelves reflect daylight onto the ceilings of interior spaces and also protect areas close to the windows from exposure to direct sunlight (Figure 1 b). Solar glazing The 1970s saw the introduction of solar glazing. This type of glass is coated to filter out thermal radiation and the infrared spectral range of sunlight. However, the glass often has a strong dimming effect, making interior spaces appear gloomy, especially when the weather is bad. It has a mirror-like appearance on the outside and can cause glare in neighbouring buildings. Also available is glass with a reduced dimming effect and an appearance closer to clear glass, but this is less effective. It is often used in skylights and glazed roofs of halls. Stove-enamelled glass offers many variations and can be applied as a partial or graduated coating. A fine grid on a glazed roof is hardly visible from below and does not appreciably influence the transparency of the glass. Louvres and Venetian blinds Horizontal louvres and Venetian blinds enable precise control of light. Sunlight

Simple daylight control Light deflecting louvres and Venetian blinds Lighting-control glass for roofs or facades Heliostat for light deflection Model simulation of New Mercedes Benz Museum, Stuttgart (see p. 57ff) Architects: UN Studio van Berkel & Bos, Amsterdam Daylight Design: Transsolar Energietechnik and ULRIKE BRANDI LICHT

can be entirely filtered out or deflected onto the ceiling in order to direct it far into an interior space (Figure 2). Various materials for coating the slats are available and can enhance this effect. External blinds are susceptible to wind damage but internal blinds are less effective in terms of thermal protection. Venetian blinds can also be fixed in the cavity of double-glazing where they do not collect dirt as easily. Louvres on the facade – made of anodised aluminium or glass – can take on larger dimensions and a variety of cross-sections. The arched, reflecting surface fans out the light. Lighting-control glass There are several systems that use the space between the panes of double-glazing to accommodate optimised optical objects and profiles. Light-control glass is filled with acrylic sections that deflect light onto the ceiling of an interior space by means of total reflection within the acrylic material. An additional prismatic contouring of the inner pane of glass helps to distribute lower altitude light in a room (Figure 3). Prismatic sheets in double glazing Prismatic sheets also rely on total reflection in acrylic glass: While direct sunlight is reflected back to the outside or against the ceiling of an interior space, diffuse light from the sky passes through the material. Prismatic sheets are used in windows and skylights. They can be combined in up to three layers of differently shaped prisms and are occasionally used with partially mirror-evaporated prism sides to guarantee protection against solar radiation, glare and deflection for various positions of the sun. However, they are expensive and absorb much light, hence, lighting designers have been searching for alternative methods. Prism slats are of simpler construction and may 43

Light for the Public Utility Company in Schönebeck Ulrike Brandi

The Public Utility Company in Schönebeck wanted a new energy-efficient building. Clever design with daylight can have an impact here, just as it can improve the quality of light in workplaces. Severe traffic pollution at the site, building regulations, and the company’s ecological objectives led to the design of a compact inward-facing building. Two solid building sections flank a glazed hall that forms the centre in terms of function, energy and daylight. Facing the interior space are offices, counter workplaces and circulation areas (waiting zone and exhibition space on the ground floor, cafeteria on the first floor and an auditorium on the second floor), while the secondary functions, such as sanitary facilities, copy and storage rooms, are located, as a “buffer”, in the outer zones of the solid building sections.

Client: Stadtwerke Schönebeck Architects: Günther Haß and Stefan Rimpf, Eckernförde Artificial lighting and daylight design: ULRIKE BRANDI LICHT

Daylight We studied the light radiation penetrating the glazed atrium (Figures 2 – 7) to ascertain whether the workplaces would obtain sufficient amounts of daylight, whether the sunlight would lead to unacceptable levels of glare and heat gain, and as the case may be to establish measures to improve the situation. We found that the east-west orientation of the hall and the southerly incline of the glazed roof generally suited the utilisation concept of the building. The sunlight penetrating the glazed roof at a steep angle permits the desired solar gain and offers a lively abundance of light in the atrium. At the same time, discomfort at the workplaces is negligible as sunlight mainly falls onto circulation spaces. The use of colour-neutral solar glazing in combination with printed panes in the roof (white dot screen with 30 % shading), in conjunction with the thermal storage properties of the solid building sections and a ventilation concept, are sufficient to

ensure a pleasant indoor climate. Even in the problematic glazed entrance area to the west (low altitude of the sun in the afternoon) it could be demonstrated that apart form solar glazing no additional measures, such as external louvres, would have to be taken. The floor plan helped: the lift core next to the entrance and the projecting oriel shield the office areas beyond from glare. The orientation of the EDP workplaces towards the hall also prevents glare, as the light comes from the side, not from the front or back of the screens. We also examined the possibility of directing more daylight into the building. The west facade in particular, where office workplaces are located, would be suitable for deflecting daylight using holographic optical elements or light-deflecting louvres in the interspace of double glazing. The cost-benefit analysis results were not convincing. Due to its favourable geometry, the central atrium of the Public Utility Company in Schönebeck receives high levels of daylight during working hours, only rarely requiring artificial lights to be switched on. The concept of a glass hall flooded with light, forming the green heart of the building, could be implemented with a relatively low technical input; and because the findings of the daylight analysis were incorporated at the design stage.

Public Utility Company Schönebeck

Public Utility Company in Schönebeck, west facade 2–4 The sections illustrate the direct incident solar radiation through the south facing glass roof throughout the seasons and days. It shows that adverse optical effects are negligible in the workplaces because sunlight mainly hits the circulation areas. 5–7 The solar radiation on the east and west facade can be checked in plan. Sunlight hits the EDP workplaces oriented towards the glazed hall laterally, that is, neither from the front nor from behind, causing only marginal glare. Parts of the building (lift core and projection) shade the workplaces to a great extent from the critical, low altitude sun.

Public Utility Company Schรถnebeck

Public Utility Company SchĂśnebeck

Artificial light The hall The impression created by illumination of the generously proportioned hall is accomplished by lighting the two flanking office tracts. Bright ceilings visually extend the atrium and create a friendly atmosphere. Scaled-down inconspicuous pendant luminaires achieve, with a combination of direct and indirect light, bright ceilings and differentiated pleasant light for working in. The luminaires, positioned perpendicular to the axis of the hall, are slender in appearance and do not obstruct the view into the space beyond. The light in the galleriesâ&#x20AC;&#x2122; circulation areas is different from that of the offices: surface-mounted downlights with softly deflecting diffuse glass are visible light sources lined up beneath the galleries. The pendant luminaires that provide the general lighting in the hall do not disrupt the impression of the space. They are sober and technical in character. The walls flanking the entrance area to the west are lit from below by recessed floor luminaires and by surface-mounted spotlights from the top, giving emphasis to the entry zone. In the evening ambience, small spotlights beneath the glazed roof highlight its construction, thereby marking the limits of the space. Recessed floor lights illuminate the trees to create a special atmosphere for nighttime events. Light points on the pool amplify the movement of the water, adding a playful and lively aspect that even extends to the exterior.

tors in the luminaires. Compact fluorescent lamps intensify the effect. An inconspicuously placed line of light along the skylight and the band of windows the length of the outside wall emphasise this area in the evening. Cafeteria Downlights with opal covers alternate with pendant luminaires to create atmospheric light in the cafeteria. Where the gallery meets the cafeteria, the gallery lighting is deliberately continued to maintain its clarity when seen from the hall. The sanitary facilities receive light from diffuse deflecting surface-mounted luminaires in combination with two vertical luminaires mounted on either side of the mirror. Auxiliary rooms are lit by fluorescent luminaires with opal covers. External stairs Recessed wall luminaires brighten the underside of the steps above and highlight the verticality as viewed from the outside. Fluorescent lamps and high pressure discharge lamps were predominantly used as were light diodes, which are energy-efficient and low maintenance. In some areas additional luminaires with tungsten halogen lamps were fitted for extra brilliant light. The luminaires are controlled and adjusted via an EIB system.

Office areas The light of the office spaces, with pendant luminaires, has been described above. It is supplemented by surfacemounted downlights which are visible only as round light apertures. These shed a wash of light from above across the rear walls of the offices and limit the space as seen from the hall. Due to the backlighting, the fully glazed north-west facade maintains a strong presence in the streetscape. 8

The auditorium Two lighting systems integrated into the ceiling, create both sober light for meetings and lectures and festive light for nighttime events. The latter is emitted from dimmable recessed luminaires; the former is reflected by large white reflec-

a, b Public Utility Company SchĂśnebeck, Atrium One of the determining factors of the light ambience in the hall was the choice of solar glazing. Only colour-neutral glass prevents distortion of natural colours and also artificial light colours as well as other unwanted effects (often a greenish tinge). Panes in the roof glazing are printed with a fine white dot screen shading 30 % of the area. They are hardly visible from below and do not obscure the transparency of the glass.

Light and Shadow – Design of a Church Christina Augustesen

Attuning a design to daylight requires incorporating the animated play of shadows. Shadows as strong design elements that have yet to receive enough attention. Depending on the light incidence shadows can move, intensify, or produce different colour effects in the eye of the beholder. While artificial light is generally static and almost like a snapshot, a continually changing light ambience is alive. What is shadow? Shadow is, according to the metaphor, “a hole in the light, something absent”. The light seems to be absent, but the shadow proves the existence of light by negating it. Near shadows, light has only one direction. Shadows describe the appearance of the objects that have cast them. This leads to active moments of perception, although the shadow remains passive. The object produces the shadow, and as the object moves, the shadow changes, not vice versa. Shadows are always twodimensional; they fall onto surfaces which may well form part of a spatial arrangement. If space on a horizontal plane is not sufficient, the shadow will transfer to an inclined or vertical plane behind. Shadow does not have a predetermined direction or predefined shape, it is pliant.

light will draw a sharply outlined silhouette; diffuse light of the overcast sky hardly produces shadows at all. When daylight fades so do the shadows and the illuminated room will retain its contours. The shadows in a room are the result of sunlight passing through the window with its glazing bars, across the furniture, colours and surfaces and into the room. Shadows vary according to the position of sunlight, following in sequence. The shadows of visitors are superimposed; their shadows overlap with the shadows of the objects in the room, blending into one image. Some shadows can be calculated in advance. However, other shadows can quickly alter their shape, while always remaining a mystery to the eye; they succeed in fascinating us.

The mystery of shadows and the quality of daylight were the source of inspiration for the design of the church in Trekroner, Denmark.

If the shadow falls onto differently positioned surfaces, horizontal or vertical for example, a separate spatial impression is perceived in each situation. Light and darkness produce diverse spatial effects. Spaces that are alive with moving shadows will be perceived in a more differentiated manner than spaces with fixed lighting. Shadows occur fleetingly and can quickly change. The shadow follows the occurrence of light and intensifies in parallel to its expressiveness. A direct ray of sun52

1–4 Light studies using 3D computer models are an important instrument in the design process to examine different alternatives. 5 Sectional elevation facing altar 6 Sectional elevation facing organ 7 Floor plan 8 Longitudinal section

Light and shadow

Concept The space of the church is of a simple composition. The liveliness is produced by the incidence of light and the resultant shadows which change continuously. Thus the design follows the traditions of religious architecture. Light, as a possible metaphor, makes the church accessible to the believer as a worldly manifestation of divinity; it describes the cycle of life in a daily recurring rhythm of light incidence in its endless variations. The space was conceived as a â&#x20AC;&#x153;protective coverâ&#x20AC;? to provide the visitor with a safe environment for prayer and concentration. The universe is present in the shadows . Rhythm and repetition are important elements for Christians in finding a deeper relationship with themselves and the divinity. In this sense, the design is traditional: The rhythm of the structure creates light and shadow in a cycle of daily renewable nuances. Light and spatial structure The church is sited according to Christian tradition along the points of the compass: the longitudinal facades are north-south orientated, the vestibule to the west and the chancel to the east. The exterior of the church is shaped like a glass cube held by the closed ends at the vestibule (14 m in height) and the chancel (19 m in height). In the interior, the supporting timber construction arches like a perforated shell across the church space, its effect constantly changing with the shadows. Heavy concrete walls, with 4 to 5 metrehigh steps that could be described as side aisles, enclose the lower third of the space. The steps can be used for additional seating and form the southern part of the gallery which can be reached from the vestibule. The opaque sections of the interior walls are projection surfaces for

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Vestibule Baptistery Chapel Altar Sacristy

Light and shadow

Sunlight in direction of altar

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Sunlight in direction of organ

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the respective shadows and direct the view towards the sky. The closed parts of the structure in the west comprise the vestibule, baptistery and the stairwell to the balcony which houses the organ. A skylight illuminates the stairs and accentuates the vestibule. Unobstructed views from the baptistery into the church and to the north facade are afforded through a glazed wall. The entrance to the lectern and sacristy is to the east, with an extra room for the priests. Light falls through a large window in the east facade onto a row of lamellae in a partition wall between sacristy and church. This provides indirect lighting, depending on the angle of incidence, for the altar. Behind the light-reflecting lamellae one can step outside into the arcades along the south facade. True to their nature they are the transition zone from interior to exterior and serve as a mingling place for people before and after the service. The priests have direct access to this area from the sacristy and can use the space for open-air services. In the northeast of the church there is a small chapel. It receives direct light from the north. This light creates the necessary contrast to the diffuse light falling through 54

the translucent facade and ceiling in the main church. From the chapel one has an unobstructed view of a woodland belt to the north of the site. The two characteristic materials in the interior are concrete and wood. The fairfaced concrete of the walls and floor conveys a feeling of security and weight to “protect” the churchgoers from the underworld. The polished surface reflects the light. The material of the lightweight timber construction gives the space a warm, organic atmosphere. Daylight The church is bathed in soft, intricate daylight, the result of interplay between the translucent glass facade and glass ceiling. Only the glazing in the west facade and the windows in the small chapel have transparent glass. The outer skin of the church filters much of the daylight and simultaneously creates a play of shadows in the interior, varied through the course of the day. On a sunny day in June the following light situations may be observed: The morning sun, shining into the large window of the sacristy from the east, is reflected by the horizontal light lamellae

and then appears in the church as golden soft light, like a “carpet of light” behind the altar in the chancel. During the course of the service the sun will move south resulting in long shadows being cast through the timber beams and across the interior of the church. At midday, the white light is still in the chancel, and a “sea” of speckled light and shadow on the wall vestibule wall will be noticed. The afternoon light draws new and longer shadows towards the altar, “embraces” the space to the west and nearly fills the entire room with light. Low shadows extend along the north and south walls and emphasise the horizontal plane of the platforms. The red and purple nuances of the imminent sundown shimmer through the transparent west facade and tinge the timber columns in these light colours. The path of the sun creates continuously changing shadows in the church space. The intensity of the shadow may increase or decrease with the cloud cover. The church can also be “shadowless”, a naked space without directed light, but moments later the light situation will have changed completely. In the wintertime the days in northern Europe are short. The sun is low in the

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sky, producing long shadows and thus different shadow spaces. The tall closed wall on the south facade prevents shadows from forming on the floor. The subdued light ambience of winter can be felt in the interior through the churchâ&#x20AC;&#x2122;s transparent skin. One can still see the light in the chancel, but at a different time of day than in summer, and not at Eucharist. Artificial light During some seasons and also mornings and evenings, daylight is not sufficient to illuminate the church, and artificial light is required. Daylight and artificial light have different qualities. Thus, a separate concept was developed for artificial light. The church is intentionally lit to create a different result: the realised lighting concept included luminaires in the pews, in the timber structure and behind the altar. Three dimmable spots constitute the basic illumination of the timber beam structure. The light is lost along the rafters in the upper area of the church, which is obscured in darkness. The lamellae of the altar wall are also backlit with dimmable spots so that brightness in the altar space can be adjusted to the occasion. The light in the pews is for reading only. The warm-

white light tone of all the luminaries creates an atmosphere of security. Artificial light also casts shadows, but these are static because the light source does not move. They can be diffuse or contrasting, depending on the power and position of the light source that produces them. However, the shadows created by the spots in the timber construction are more diffuse than those produced by sunlight. Lighting design was not an afterthought; instead the different light situations and their inherent rhythms formed the basis of the design of this building. The design principle implemented here is a fitting example of the significant role light plays in architecture: â&#x20AC;&#x153;There is no space without light and there is no form without light. What is architecture without space and form?â&#x20AC;? (I. M. Pei). 9

With the help of 3D computer simulations different light situations were simulated for a sunny day in June. The pictures were taken at intervals of two hours, firstly facing the altar and then facing the organ. The last two images show the church space in December. Next page: Wooden model of the final design at a scale of 1:50 to analyse the results in a light laboratory beneath an artificial sky.

Procedure for Planning Artificial Light in Buildings Christoph Geissmar-Brandi

Prerequisite Lighting design of interior spaces by professionals is a wholehearted, enjoyable pursuit. The result is the designed light ambience which has an effect on the wellbeing of the people who live and work or spend their free time in a building. The development of a successful scheme can only be achieved by a team, and requires in-depth knowledge and good communication skills of all its members. The aim of a good lighting proposal is to optimise in both technical and economic terms a scheme in combination with the following fundamental “vital” principles: • Light reinforces the idea, the vision or soul of a space, • the proposed light is compatible with the function of the building and meets expectations regarding the use of its interior spaces, • the proposed system must be technically and economically optimised and thus within a reasonable budget, • following the above three principles will ensure that the light is appropriate for the interior spaces, also in its respective details. In essence this means that for each building project a new and individual solution must be developed in consultation with client, architects and electrical engineers, that puts into practice, to a high aesthetic standard, the functional and design objectives for the proposed building. The designed lighting system should be more economical than a standard solution, and should be made to last. The lighting designer should consider several aspects, including • light as a material, and • light as a medium for visual communication. 70

Of equal importance is a comprehensive understanding of the entire building, its formal composition and technical systems, ceilings and facades, right down to the requirements and constraints of specific rooms. Since lighting is often scheduled at the end of the design process, good communication between all the consultants involved, and mutual respect for each other’s work, is essential. If communication fails, the often high expectations do not match the reality of costs. When lighting designers are involved from the beginning of the design process, and when their wide experience of the effect of light on interior spaces (irrespective of the computable data) is utilised, their input can contribute significantly to the functional and spatial aesthetic optimisation of a building. Light as a material What we see is made visible by reflected light. Hence, the objective of a design proposal is not just light itself, but also the surfaces on which it falls. Information on the proposed surface materials and the reflective properties of floors, walls and ceilings is indispensable to the planning process; with it the designer can ascertain the brightness and the appearance of the room as well as its ambience. The proposed colour scheme is a further important aspect to be considered in the design of lighting. Dark colours “swallow” light, bright hues are better in this respect as they reflect light. In the calculation of the size of a lighting system the effect of colour and reflective, or matt characteristics of a material, are still a matter of experience. Without this experience the designer tends to over-dimension the system to be on the safe side.

Procedure for planning artificial light

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Light as a medium of visual (visible) communication Perception of our environment is very much influenced by the respective lighting conditions; light is one of the main factors in determining the atmosphere of a space. In the assessment of buildings sophisticated lighting is considered as one of the “soft” qualities, which is not easily quantified, and, it may even be necessary to bring it to the client’s or user’s attention. The client’s selection of a specific architect and a specific lighting designer, and his expectations with regard to their designs, communicate a specific intention. Whether it be a private investor, contractor or public institution, his choice conveys a whole spectrum of qualities such as openness or discretion, clarity, transparency, a feeling of security, respect for staff and guests and the wish for either innovation or tradition. The architecture will reveal these predilections. This could be described as “vibes”; the light responds, enhances and emphasises – architecture and light interact. The following tools are available to the lighting designer: • warm – cold light • brilliant – diffuse light • contrasting light (casting shadows) – soft light • static light – movable light • focussed light – general light • daylight and artificial light • in rare instances coloured light. Different light ambiences of a room depend on changes in daylight and adjustments of the artificial lighting situation. Our (light) requirements differ; in the evening we want warm light, but during the day we can best concentrate in bright, clear, fresh and abundant light.

Lighting designers may have different opinions on how to handle light in buildings. They either integrate light into the architecture or seek visual dominance. The integrative approach prefers soft, sensitive light in all its nuances. The domineering approach demands strong, loud and colourful light. It is decorative, an accessory, sometimes contrived, often using appliquéd light objects. A third approach employs cool, anonymous light. These approaches suit different architects, or rather their buildings. It is thus advisable for consultants who have compatible views to establish long-term working relationships. Tasks of the lighting designer First and foremost, lighting designers need to plan in cooperation with clients, architects, and various engineers; therefore technical know-how and competent design skills are required – and in fact both are necessary for good lighting design. The design of artificial lighting touches on all stages of the design process. It is thus important to have a systematic, step-by-step approach due to the often long time spans from commencement to completion. The result is not in evidence until the very end of the process when the building has been completed and it starts to “shine”. It is only at this point that the expectations of the client, the architects and M & E engineers are fulfilled, the toil and limitation imposed by a small lighting budget forgotten. Architects and clients define the building in terms of • function and client/user requirements, • interior space (height, width, depth), • its relation to daylight, • facade, • surfaces of ceiling, walls and floor, • colours, and

Design sketch of artificial lighting, atrium, New Mercedes Benz Museum, Stuttgart

• standards of mechanical and electrical engineering, especially of electrical equipment. The lighting designer’s proposal is determined by • light characteristics, • light colours, • light heights, • light scenes, in consideration of technical constraints that are based upon experience or on standards and regulations. The components of the proposed lighting system are • lamps, • luminaries and reflectors, • possibilities for their installation and future maintenance, • circuit and wiring including ballast, • circuit options, and • emergency lighting. Design process In simplified terms, the lighting design process falls into a design stage and a production information stage. Planning permission is generally not required for lighting, except for proposals on facades (advertisements). Initially, the design describes the light character and the type of lamp (for example, “indirect wash onto the ceiling”). The specification of the product and the setting-out of its location will be done at the production information stage. Lighting tests play a central role in this context. They can be carried out on existing buildings (facade lighting), in show rooms or in mock-ups (1:1 simulations) at the manufacturer’s offices. They are necessary for the correct assessment of proposed lighting effects. Considerable cost savings can be achieved by reducing systems that have been correctly calculated, but are in fact over-dimensioned, or 71

Designing artificial light

by avoiding refitting or modification of a system at a later date.

specified. It is not the role of the consultant lighting designer to draw plans necessary for construction. The “transfer” of the lighting proposal into the production information is the responsibility of the architects and engineers, as is the keeping to deadlines and budgets. To a large extent, the effective use of the lighting consultant’s advisory service depends on their commitment and competence.

Scope of the appointment The degree to which the lighting consultant is involved beyond the concept stage, in the selection of products and the actual construction process, depends on the type and scope of his appointment. Contracts limited to design services are becoming increasingly widespread. The choice of product is then a question of cost, and will become the responsibility of the electrical engineers, rather than the task of the lighting designer. The outcome of his work depends on whether he was engaged as a lighting designer or as an adviser.

Designing artificial light How does one proceed? Again, there is the question of the task as well as of individual skills. To find the appropriate light-

Lighting designers will produce CAD drawings for the entire building (auxiliary rooms and plant rooms are often omitted for practical reasons). The architects or the electrical engineers provide the plans onto which he adds the luminaires. The degree of accuracy of the positions and products shown on the plans depends on the progress of the job, and on the detail of the respective drawings. Early on, drawings will merely show the rough positions of luminaires; at the final stage, luminaires are accurately specified including information on accessories, quantities and on their setting-out. As consultant, a lighting designer will develop a concept for either the entire building or for specific areas of that building. He will then discuss his outline proposal with the architects and engineers, and will make necessary adjustments. Illustrations are used to describe the intended lighting effect. At this concept stage the luminaire positions, heights and illuminance levels must be established; luminaire types and light colours are also stated, but the product itself is not yet 72

ing design solution for an exceptional building requires the trust of the client and architect, and usually a higher design input by the lighting consultant. Apart from such special jobs there are “normal” projects, generally presumed to be simple, that require the development of a professionally sound concept for specific rooms. These projects are often a challenge for lighting designers because they are run on tight construction budgets. A good lighting design proposal is based on in-depth knowledge of the building. This can be difficult to achieve since clients

Procedure for planning artificial light

and architects sometimes have divergent expectations. They hire consultants to help with the technical realisation of their ideas, to openly discuss them or to enhance existing designs with the use of light. The design process starts with an imaginary tour of the building. First of all lighting designers will, in their mind’s eye, record the daylight apertures and the directions of users’ views. Information on the building’s siting is collected, also on the orientation of windows, neighbouring buildings, vegetation and the time of use. These activities are part of the preliminary services and the outline proposal stage. The design concept is defined once the proposed function of a space is combined with a lighting idea. Most of the light we perceive is indirect light that is reflected onto the retina. The first step in the development of a design should be the assessment of the surface properties of the room. Its “furnishing” is also an important factor: a reading room has a certain type of light different from that of a hospital ward or a car museum. Light is specifically designed for different uses – even those within one room – taking into consideration the effect of colours and surfaces. In technical terms, this effect is measured as reflectance, a factor in the calculation of the necessary “light levels”. In this way the first mental sketch of the design evolves. Once the general idea of what areas need to be lit has been established, the rough positioning of the luminaires can be done and the luminaire types defined. The feasibility of these first ideas should be tested straight away. Proof of the expertise of a consultant lies in how far he is able to transpose a good design into a clear-cut system. If the design is feasible

in terms of ceilings, walls and floors, surface materials, cable runs, other aspects of M&E engineering, and apertures for windows and doors, then the necessary quantities of luminaires can be estimated and a rough calculation of the illuminance made. Generally, two to three different types of light will be employed, for example, vertical illumination, direct accent light and general illumination. The choice of luminaire depends on the type of lamp it operates. This interdependence arises from formal (aesthetic), technical and economic considerations. Finally, the circuits, including switches and alternative controls for the different system options, need to be defined. Emergency lighting is designed concurrently. Information on the types and quantities of luminaires, lamps and circuits, their installation and the required accessory devices is collected to produce a preliminary estimate of the proposal, and to work out its subsequent operating costs. Irrespective of this, as the project progresses, it becomes increasingly important to make sure the scheme is within budget – and of course fundamental to the success of the concept.

prior to approval. Amendments pose a problem for job profitability because it is generally expected that these are done at no additional cost to the client – and they can be time-consuming. Legal aspects of this problem are discussed in the section “The Lighting Designer’s Position from a Contractual Point of View” (see pp. 84ff).

A lighting designer who from the outset incorporates existing standards and regulations may also achieve good results. Generally, standards are recommendations, but in a commercial context and in conjunction with workplace directives, they are essentially binding. Other regulations, for example emergency lighting, must always be adhered to. The final proposal stage entails the coordination of architects and engineers, and the presentation of the design to the client which then needs to be approved. Often the user, architect or the client requests amendments to the scheme

2–4 Photographs and drawings of the cloud luminaire for the ceiling of the collection area, New Mercedes Benz Museum, Stuttgart (see p. 57ff) Architects: UN Studio van Berkel & Bos, Amsterdam Daylight design: Transsolar Energietechnik and ULRIKE BRANDI LICHT

Daylight as a building material

Daylight as a Building Material Merete Madsen Peter Thule Kristensen

Daylight is one of the central themes of 20th century architecture. Daylight is not merely a means of bringing light into a building, or a traditional symbol of divinity; daylight is a building material in its own right that is celebrated in architecture. At the same time daylight is increasingly employed to create and dissolve space. Since the beginning of the century, space is no longer merely looked upon as a void surrounded by walls, but as something that stands alone – as infinite abundance. It is daylight that can shape an uncontoured space in an almost material way – just as it can make a fleeting ray of light turn an instant into an intense experience. The space takes on a peculiar meaning – as demonstrated in the paintings by the Danish artist Vilhelm Hammershøi (Figure 1). In the same vein, the significance of daylight does not stem primarily from functional and physiological factors, as proclaimed by functionalism. In many of the major buildings of the 20th century daylight is also employed to create ambience and movement, to articulate the space in a new way.

As early as the 19th century values and symbols had become increasingly fleeting and the known system of the world, hitherto considered eternal, deteriorated; in architecture, traditional positions were called into question, as well. This was a challenge to architects’ creativity, artistic energy and their urge to experiment – light and space were explored as independent phenomena. It is interesting to trace how daylight turns into a “building material” that contributes to shaping modern spaces. What kinds of spaces are designed by daylight and its companion the shadow? How can daylight contribute to lending these spaces a special, spiritual atmosphere that is difficult to communicate in our fast-moving 92

world and in the absence of a generally recognised, traditional or religious visual language? The selection of the following European examples will illustrate how the building material daylight was discovered and utilised in the 20th century: in the buildings by Mies van der Rohe and Le Corbusier daylight is used to emphasise spatial complexity, with the help of reflection or by intricate interaction of several simultaneous light sources. In the works of other architects one can find examples in which sidelighting becomes a design element in its own right, or of broken light obtaining a spiritual character. We will see further examples of daylight used to localise places in an otherwise open interior space, or of cast shadows lending a sign-like character. Finally there are examples of how soft daylight can create almost weightless spaces. The projects are in chronological order, and conclude with an overview of current trends. Light reflex The characteristic of glass to create spatial links with transparency became an important design element of many 20th century architects. One source of inspiration was the industrial architecture of the 19th century with its new building materials and the resultant structural possibilities, such as steel construction making it possible to design large glazed areas. Glass can also reflect the surroundings and obscure the effects of light and shadow that otherwise emphasise space and form. The German architect Mies van der Rohe utilised this effect. In his exhibition pavilion in Barcelona (1928–29) coloured glass walls form a strong, expressive element that filters daylight while reflecting the surroundings (Figure 2). In the pavilion, the characteristic of daylight to accentuate specific areas with cast shadows is of

Daylight as a building material

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“Dust motes dancing in sunlight”, VilhelmHammershøi, 1900 Light reflexes, German Pavilion, International Exhibition Barcelona, 1928–29; Architect: Ludwig Mies van der Rohe

Daylight as a building material

less importance than exploiting daylight reflexes to create spatial ambiguity. Daylight is utilised to create an artful interplay of the coloured shadows cast by glass walls, reflections on glass surfaces, on the dyed natural stone walls, bare steel columns, and in a large pool of water. The changeability of daylight adds an extra layer to this simple yet spatially complex composition. When moving through the pavilion constantly changing views are revealed and reflections overlie spatial impressions – transparency and light reflexes create dissimilar and shifting spatial connections. Intersecting light The Barcelona Pavilion breaks with the traditions of classical design whereby the visitor obtains a general overview from the centre of the composition. Only by physically moving through the building can the visitor grasp the space in its entirety. The combination of space and movement is a theme of many 20th century architects, especially the Swiss architect and painter Le Corbusier, who liked to use daylight in arrangements of spatial ambiguity. These are rarely expressed in the form of daylight reflections on glass, but rather the interplay of competing sources of daylight that stimulate movement and create rooms with multi-faceted spaces and impressions. This can also be seen in Le Corbusier’s own apartment at the top of the Port Molitor Building in Paris (1931–34). In the foyer one can detect several daylight apertures: A cut-out in the ceiling above the stairs and a glass wall in the space beyond mark possible end points of intersecting lines of movement while a horizontal band of windows in the foyer underlines its passage-like character (Figure 3). The stairs are lit from different sides; the boundaries of the space are blurred. Light from the various apertures is superimposed when hitting the sculptural, freestanding, curved flight of stairs. The composition brings to mind a cubist painting in which the motif is observed from several viewpoints simultaneously. Sidelight The two examples from Barcelona and Paris represent an architectural style that uses daylight to stage a completely new form of spatial design. Architecture in Scandinavian countries is hardly ever this radical, but more attention is paid to utilising daylight as such; because Nordic light is less intense and thus a precious

building material. Northern architects have to work with diffuse, weak light that is generally emitted from an overcast sky. They consider light to be something special and use it accordingly; at times it borders on the spiritual or metaphysical. One example is the funeral chapel in Turku, Finnland (1939–41) by the Finnish architect Erik Bryggman. In the middle of the day, a sidelight enters the chapel through a concealed opening and falls onto the back wall of the altar niche (Figure 4). Entering diagonally from above, it seems to belong to another world. Its religious character is emphasised by the fact that other light sources are visible. They either shine from below through the side aisles or through small openings in the dark vaults of the nave, which dramatically frame the bright altar niche. The sidelight is arranged as a changing “object”, a substitute for the traditional altar screen. Through the side aisle one can see the tree trunks in the woodland outside, and thus the explicit focus on the altar is disrupted by an asymmetrical gesture. The worshipper is in a space between “mundane and heavenly” light.

Daylight as a building material

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Intersecting light, Apartment Le Corbusier, Paris, 1931â&#x20AC;&#x201C;34; Architect: Le Corbusier Sidelight, Funeral Chapel, Turku, Finland, 1939 â&#x20AC;&#x201C; 41; Architect: Erik Bryggman